This invention relates generally to balancers for internal combustion engines. More particularly, this invention relates to balancer shafts of a novel configuration.
The use of balance shafts in an internal combustion engine is well known in the prior art. A balance shaft is a counterweighted shaft, typically driven by the crankshaft either directly or through a mechanical link. As a result, the balance shaft balances out first or second order forces and/or moments in a reciprocating machine, e.g., a typical internal combustion engine, encountered during operation of the engine.
There is a myriad of well known balance shaft designs used in the industry to address imbalances. Typically, the prior art balancer shafts are solid bars or beams, solid steel beams, or tube designs that have a solid half-circle or semi-circular cross-section with a certain thickness that runs the length of the balance shaft. However, these balancer shafts designs result in higher mass quantities, which lead to greater overall engine weight and production costs. The higher balancer shaft mass is undesirable to engine design and the higher weight also adversely affects engine performance characteristics.
There is a thus a need for a reduced mass balancer shaft that will effectively balance first or second order imbalances in an internal combustion engine, thereby decreasing overall engine mass.
The present invention provides a reduced mass balancer shaft that effectively balance first or second order engine imbalances in an internal combustion engine. The reduced mass balancer shaft decreases overall engine mass. The balancer shaft is symmetrical with offset masses that are equal in magnitude and opposite in direction and orientation. The balancer shaft preferably comprises a front offset mass between a front journal and a center section, and a rear offset mass between the center section and a rear journal. In a preferred embodiment, there are two integrally formed stiffening members with the front and rear offset masses respectively and symmetric about the balancer shaft centerline. The front and rear offset masses are each comprised of partial annular configurations that extend a degree range of about 165 to 195 degrees, and where the front and rear offset mass extend equally away from the balancer shaft centerline. The center section is comprised of an annular configuration.
The following drawings and description set forth additional advantages and benefits of the invention. More advantages and benefits will be obvious from the description and may be learned by practice of the invention.